Materials for the manufacture of foundry molds and cores



Nov. 26, 1968 H. THAMLITZ 3,413,251

MATERIALS FOR THE MANUFACTURE OF FOUNDRY MOLDS AND CORES Filed Aug. 26,1964 TENS/LE STRENGTH, PSI

TIME, HOURS (MIXTURE 2 United States Patent "ice 3,413,251 MATERIALS FORTHE MANUFACTURE OF FOUNDRY MOLDS AND CORES Heinz Thamlitz, Kaarst, nearNeuss, Germany, assignor to Gebr. Huttenes Kommanditgesellschaft,Dusseldorf- Heerdt, Germany Filed Aug. 26, 1964, Ser. No. 392,190 Claimspriority, application Germany, Sept. 20, 1963, H 50,314 6 Claims. (Cl.26024) ABSTRACT OF THE DISCLOSURE Method of producing mixtures suitablefor the production of foundry molds and cores comprises adding to amixture of wet foundry sand and hydrophilic binder of thermosettingsynthetic resin such as furan resin a small amount of hydrophibicsubstance such as tall oil distillation residues, situmes, and fat acidpitches.

This invention relates to methods and materials for the manufacture offoundry molds and cores and particularly to a method and material formanufacturing foundry molds and cores with hydrophilic binders which areunaffected by moisture.

Methods and materials for the manufacture of foundry cores and molds aregenerally known. They fall basically into two types: (1) those that usehydrophobic binders and (2) those that use hydrophilic binders.

Cores and molds of both these types in the hardened condition aregenerally of satisfactory strength but are often very sensitive tomoisture. This is a serious disadvantage because it is usually desiredto produce a cast product from such molds which has a smooth, cleansurface. In order to accomplish this, it is conventional to wash thesurface of the mold or core with an aqueous suspension or slime of aninorganic or organic material such as quartz sand, zirconium sand flour,clay, graphite coal dust or the like material with small amounts of awater soluble binder. This coating or wash may be applied by dipping thecores into the aqueous mixture, or by spraying or painting the aqueousmixture onto the surfaces of the cores and molds. The washed cores ormolds are then dried in order to remove the water, generally in afurnace. It has been found that this practice of washing the mold orcore substantially reduces the strength of a mold or core of thehydrophilic type.

The present invention overcomes this problem of reduction in strength bymoisture effect on molds and cores produced from wet sand mixtures withhydrophilic binding agents. According to the present invention, thisimprovement is attained by the addition of a small amount of hydrophobicor water repellent agent into the sand-hydrophilic binder admixture.This improvement is attained by adding 0.01% to 2% of a hydrophobic orwater repellent agent to the sand and binder mixture or about 1% to 10%of such hydrophobic agent to the hydrophilic binder.

The invention is based upon the unexpected and surprising discovery thatwet sand mixtures with a hydrophilic binder such as the hydrophilicresin binders may be insensitive to moisture by the addition of smallamounts of hydrophobic materials so that moulds and cores made therefromafter being baked retain their strength even after washing with aqueouswashes or slimes. Among the hydrophobic substances which have been foundto be advantageous in the practice of this invention are solutions ofbitumes, bituminous materials, the distillation residues of fatty acids,the distillation residues of tall oil and similar materials.

The following examples are to show the influence of 3,413,251 PatentedNov. 26, 1968 hydrophobic substances upon the sensitivity to water ofcores and molds which before had hydrophilic properties. Variousmixtures whose compositions are given below were subjected to the sametype of test. All the mixtures were prepared in a pug mill and samplesmade of each mixture. Each sample was then stored for 24 hours, orhardened, as will be indicated below, and its tensile strengthdetermined subsequently. Thereafter, a further sample of the samemixture, after storing it for 24 hours, or hardening, was immersed inwater for 30 seconds and after superficial drying by allowing the waterto drip off for 10 seconds also subjected to a tensile strength test.

In addition to the compositions of the samples the results of the twotensile strength tests just referred to are given below. Allcompositions are given in parts by weight.

Mixture 1 Composition:

100 parts of quartz sand 0.6 part of orthophosphoric acid (acting ascatalyst).

2.0 parts of furan resin (acting as hydrophilic binder).

Tensile strengths:

710 p.s.i. before immersion.

210 p.s.i. after immersion.

Mixture 1a Composition: 100 parts of quartz sand. 0.6 part oforthophosphoric acid (acting as catalyst). 2.0 parts of furan resin(acting as hydrophilic binder). 0.3 part of a distillation residue oftall oil (acting as hydrophobic substance).

Tensile strengths:

850 p.s.i. before immersion. 570 p.s.i. after immersion.

The samples made of the above compositions, numbered 1 and 1a, werestored for 24 hours before the first tensile strength test wasconducted. As distinguished therefrom, the samples made of the followingmixtures were hardened in a heated pattern, and an aqueous solution ofNH Cl was therefore added to the mixtures to act as hardening agent.

Mixture 2 Composition: 100 parts of quartz sand. 0.4 part of aqueoussolution of NH Cl. 2.0 parts of furan resin (acting as hydrophilicbinder).

Tensile strengths: 995 p.s.i. before immersion. 500 p.s.i. afterimmersion.

Mixture 2a Composition: 100 parts of quartz sand. 0.4 part of aqueoussolution of NH Cl. 2.0 parts of furan resin (acting as hydrophilicbinder). 0.02 part of a distillation residue of tall oil (acting ashydrophobic substance).

Tensile strengths:

995 p.s.i. before immersion. 855 p.s.i. after immersion.

Mixture 2b Composition:

100 parts of quartz sand 0.4 part of aqueous solution of NH Cl 2.0 partsof a mixture containing approximately percent by weight of furan resin(acting as hydrophilic binder) and 5 percent by weight of a distillationresidue of tall oil (acting as hydrophobic substance).

Tensile strengths:

925 p.s.i. before immersion 780 p.s.i. after immersion.

A preferred embodiment of the invention comprises a hydrophilic mixtureof sand, such as Ottawa sand, with a hydrophilic resin binder, such asureaformaldehyde furfuryl alcohol, to which is added 0.01% to 0.2% ofsulphate pitch dissolved in petroleum or test benzene. This will producemolds or cores which are completely resistant to reduction of strengthwhen washed with aqueous Washes such as an aqueous suspension of zirconsand.

For the purpose of the invention, and particularly for eliminating theundesired influence of moisture on molds and cores, it has been foundthat in general satisfactory results are obtained if an amount of 0.2%of a hydrophobic material, and frequently even much less, is added to amixture of sand and hydrophilic binder.

The effects obtained by adding hydrophobic substances to the mixturesalso become evident if, as in the diagram shown in the drawing, thetensile strength is plotted vs. the time required to dry the coating ofblack wash which usually is applied to the surfaces of molds and cores.In the said diagram, Curve I shows the behavior of a sample made of theabove-mentioned Mixture 1 and Curve II that of a sample made of theabove-mentioned Mixture 2. It will be noted that Curve II shows a rathernormal and continuous drop of the tensile strength, resulting fromthermal effects, whereas, according to Curve II, the strength of therespective sample passes through a pronounced minimum value. Obviously,while the strength is at such low values the cores and molds are subjectto deformation and may even break.

In the foregoing specification, there have been set out certain examplesand preferred embodiments and practices of this invention. However, itwill be understood that this invention may be otherwise embodied withinthe scope of the following claims.

What I claim is:

1. A foundry core and mold mixture essentially com prising wet foundrysand, furan resin as hydrophilic binder, and about 0.01% to about 2% ofhydrophobic substance selected from the group consisting of solutions ofbitumes, bituminous materials, distillation residues of vegetable andanimal oils, distillation residues of fatty acids and distillationresidues of tall oil.

2. Mixture according to claim 1, wherein the hydrophobic substanceconsists of 0.01 to 0.2% of sulfate pitch solution in petroleum.

3. Mixture according to claim 1, wherein the hydrophobic substanceconsists of 0.01 to 0.2% of sulfate pitch solution in test benzine.

4. Mixture according to claim 1, essentially comprising 100 parts ofquartz sand, 06 part of orthophosphoric acid, 2.0 parts of furan resinand 0.3 part of a distillation residue of tall oil.

5. Mixture according to claim 1, essentially compris ing 100 parts ofquartz sand, 0.4 part of aqueous solution of NH C1, 2.0 parts of furanresin and 0.02 part of a distillation residue of tall oil.

6. Mixture according to claim 1, essentially comprising 100 parts ofquartz sand, 0.4 part of aqueous solution of NH CI and 2.0 parts of amixture consisting of approximately by weight of furan resin andapproximately 5% by weight of a distillation residue of tall oil.

References Cited UNITED STATES PATENTS 3,004,312 10/1961 Froberger260-38 2,988,525 6/1961 Clem 26038 2,955,336 10/1960 Horn et a1 260-282,923,989 2/ 1960 Thomson 26037 2,892,227 6/ 1959 Operhall 260392,861,307 11/1958 Froberler 26028 2,657,113 10/1953 Barlow 26028.52,586,585 2/ 1952 Wallace 260-39 FOREIGN PATENTS 730,178 5/1955 GreatBritain.

OTHER REFERENCES Varnish Constituents-Chatfield-Leonard-Hill Ltd.,London, 1953, pages 619, 634.

DONALD E. CZAJA, Primary Examiner.

C. W. IVY, Assistant Examiner.

